1. Field of the Invention
This invention relates to ice makers and in particular to means for controlling the harvesting of ice bodies from such ice makers.
2. Description of the Prior Art
One example of automatic ice maker presently in wide commercial use is the flexible tray ice maker having control circuitry as disclosed in U.S. Pat. Nos. 3,648,476 and 3,714,794, which patents are owned by the assignee hereof. As disclosed therein, a single timer motor is provided to function both as the defrost cycle timer and as the ice maker mechanism drive motor, whereby ice harvesting operations are preiodically effected.
It is conventional to connect such dual action timer motors so as to be energized continuously and thereby accumulate straight clock time. Alternatively, it has been conventional to energize such timers in such ice maker applications to run intermittently as during operation of the compressor of the refrigerator apparatus only. It is quite common to provide ice maker timing means based on compressor run time, as it is felt that the rate at which ice is formed is correlated substantially with the amount of refrigeration unit run time.
A problem arises in such compressor operation correlated ice maker timers in that the length of the ice making cycle may be excessively long where the compressor is operated infrequently, as during use of the refrigeration apparatus under low ambient temperature conditions. Further, improved efficiency insulation and energy reduction techniques employed in modern refrigeration apparatus cause the compressor run time to be reduced to such an extent that excessively long ice making cycles tend to result. It has been found that under such conditions, an undesirably low amount of ice production per day may result.
It is generally known to provide means for varying the length of a clocked ice making cycle through a manually operable switch. Thus, as shown in U.S. Pat. No. 3,423,949 of Melvin G. Leeson et al, an automatic ice cube maker includes a plurality of time switches which are operated by the timer motor so that any selected switch may be actuated to provide a choice of a 22-minute, 30-minute, or 45-minute ice production cycle followed by a four-minute ice harvest cycle. Thus, the control is arranged to provide any one of a plurality of different straight clock time controls of the ice making cycle.
William L. Fox discloses, in U.S. Pat. No. 3,449,929, a refrigerator with an automatic ice cube maker wherein operation of the ice maker timer motor is effected only when the temperature in the freezer compartment in which the ice maker is disposed is below a predetermined temperature.
Svend E. Sorensen, in U.S. Pat. No. 3,459,005 shows a selective control for an ice maker wherein an analog ice making apparatus is selectively provided with different amounts of heat during the ice making cycle so as to retard the formation of ice in the analog apparatus while allowing the main ice maker to continue to make ice in the normal manner. When the analog apparatus produces a preselected amount of ice therein, the control causes discontinuation of ice making operation of the entire mechanism and permits harvesting of ice from the main ice maker. Resultingly, the size of the ice bodies being formed in the main ice maker is a function of the selective control of the analog ice maker.
In U.S. Pat. No. 3,648,478, which patent is owned by the assignee hereof, William J. Linstromberg discloses a defrost circuit for a refrigerator. In one embodiment, the control provides continuous operation of the ice maker timer. In a different embodiment, the control provides operation of the timer only when the thermostat has closed to cause the compressor of the refrigeration apparatus to run. A defrost switch is provided for automatically connecting the timer motor for operation through the compressor motor windings during a defrost operation and for independent continuous operation during the normal refrigeration operation of the apparatus.
Thomas A. Dwyer discloses, in U.S. Pat. No. 3,964,270, an ice making machine. The apparatus includes a control having a thermostatic switch connected to a manually adjustable timer for automatically controlling the operation of the ice making machine to insure that the water to be frozen is maintained at a freezing temperature for a period of time sufficient to form the desired ice.
In U.S. Pat. No. 4,292,812 of Mitsuru Kakinuma et al, the refrigeration system includes a control device having a timer circuit selectively operable simultaneously with, or with a delay after, the start of an ice making operation to provide control of the period of time during which ice making is effected. A temperature sensing element defines an impedance which varies with variations of the ambient temperature for controlling the period of time during which an ice making operation is performed, thereby to cause the thickness of the ice being made to be constant at all times.
U.S. patent application Ser. No. 424,491, now U.S. Pat. No. 4,424,683, of Larry Manson, which application is assigned to the assignee hereof, discloses an electronically controlled ice maker in which the length of an ice making cycle is varied as a function of the sensed temperature and the operation of the refrigeration means.